What Is UEFI? (Unified Extensible Firmware Interface)

The Unified Extensible Firmware Interface loads before your OS

While older PCs initiate hardware through the Basic Input Output System, or BIOS, most computers now use an initialization system called the Unified Extensible Firmware Interface, or UEFI. There are several advantages and disadvantages to UEFI in modern PCs.

ASUS UEFI BIOS Menu
UEFI BIOS Menu. ASUSTeK

What Is UEFI?

When you first turn on your computer, it doesn't immediately start loading your operating system. On older PCs, once the Power On Self Test (POST) is completed, the BIOS then initiates the operating system's bootloader. This procedure allows the computer's various hardware components to properly communicate with one another.

The UEFI is a newer specification that defines how the hardware and software communicate within a computer system. The specification actually involves two aspects of this process: boot services and runtime services. The boot services define how the hardware will initiate the software or operating system for loading. Runtime services skip the boot processor and load applications directly from the UEFI. This approach makes it act somewhat like a stripped-down operating system by launching a browser.

UEFI hasn't completely replaced BIOS. The early specifications lacked POST or configuration options. Newer systems still require the BIOS for these purposes, but they don't offer the level of customization possible in BIOS-only systems.

Advantages of UEFI

The biggest benefit of UEFI is the lack of any specific hardware dependence. BIOS is specific to the x86 architecture. UEFI allows PCs to use processors from a different vendor even if it doesn't have the legacy x86 coding.

The other major benefit of using UEFI is that it supports several operating systems without the need for a bootloader such as LILO or GRUB. Instead, the UEFI can automatically select the appropriate partition with the operating system and load from it, resulting in faster boot times.

The UEFI also offers more user-friendly interfaces than the old text menus of the BIOS, which makes it much easier to adjust the system. In addition, the interface allows you to run limited-use web browsers and mail clients without launching a full OS.

Disadvantages of UEFI

The biggest problem with UEFI is hardware and software support. In order for it to work properly, the hardware and operating system must both support the appropriate specification. This isn't as much of a challenge with the current versions of Windows and macOS, but older operating systems such as Windows XP do not support it.

History of UEFI

UEFI is an extension of the original Extensible Firmware Interface developed by Intel. Intel debuted this hardware and software interface system when the company launched its Itanium server-processor lineup. Because of its advanced architecture and the limitations of the existing BIOS systems, engineers developed a new method for handing off the hardware to the operating system that would allow for greater flexibility. Because the Itanium wasn't a huge success, the EFI standards also languished for many years.

In 2005, the Unified EFI Forum expanded upon the original specifications developed by Intel to produce a new standard for updating the hardware and software interface. This consortium includes companies such as AMD, Apple, Dell, HP, IBM, Intel, Lenovo, and Microsoft. Even two of the largest BIOS makers, American Megatrends and Pheonix Technologies, are members.